Improving winter thermal comfort in Mediterranean buildings upgrading the envelope: an adaptive assessment based on a real survey

Renovating buildings is one of the major targets within the current European goals toward decarbonized cities in 2050. The residential stock offers extensive opportunities to achieve current energy horizons, since more than 75% of the existing buildings in the European Union are energy deficient, with poorly insulated thermal envelopes which drive indoor conditions far from current comfort standards. This paper aims to provide a protocol for forecasting the upgrading potential of this housing stock in southern Europe, particularly in Mediterranean areas, identifying the level of obsolescence and possibilities for improvement, especially in winter indoor thermal conditions, offered by standard passive strategies. Following an architectural, constructive, and energy analysis of common patterns throughout the urban stock of the southern Spanish city of Córdoba, three case studies built-in 1951–1980 – pre-dating the first Spanish regulations on thermal conditioning in buildings – were selected for the assessment. Long-term monitoring and in situ tests (i.e., infrared thermography, airtightness) recorded the performance of these buildings under real occupancy conditions, subsequently incorporating them into the calibration of simulation energy models, aiming to predict the potential improvements after implementing standard passive strategies in these buildings. Results show that building retrofits not only improve the quality of indoor thermal conditions by increasing indoor temperatures by 3–4 °C but also almost eliminate occupied hours outside the comfort range.